SUMMARY: Mice were given mexiletine (1-(2',6'dimethylphenoxy)-2-amino-propane) intraperitoneally and anticonvulsant activity determined by the maximal electroshock seizure test. Blood and brain levels of mexiletine were determined by gas-liquid chromatograph. Optically active d-benzl tartrate salts of mexiletine were made as a means of separating racemic mexiletine into its optically activity antipods. The anticonvulsant activity of mexiletine in mice is of short duration, and its rate of disappearance from plasma parallels the anticonvulsant activity. Brain levels of mexiletine are much higher than plasma levels, due to its high lipid solubility. The ED50 for mexiletine at 30 minutes following administration is 10 mg/kg and rises to 43 mg/kg at 3 hours.